Oxidized lignosulfonates as additives in oil recovery processes involving chemical recovery agents

ABSTRACT

A process for producing petroleum from subterranean formations is disclosed wherein production from the formation is obtained by driving a fluid from an injection well to a production well. The process involves injecting via the injection well into the formation an aqueous solution of oxidized lignosulfonate salt as a sacrificial agent to inhibit the deposition of surfactant and/or polymer on the reservoir matrix. The process may best be carried out by injecting the oxidized lignosulfonates into the formation through the injection well mixed with either a polymer, a surfactant solution and/or a micellar dispersion. This mixture would then be followed by a drive fluid such as water to push the chemicals to the production well.

This application is a continuation-in-part of application Ser. No.745,496, filed Nov. 26, 1976, now abandoned, which is acontinuation-in-part of application Ser. No. 715,957, filed Aug. 19,1976, and application Ser. No. 591,573, filed June 30, 1975, both nowabandoned and application Ser. No. 591,574, filed June 30, 1975, nowU.S. Pat. No. 4,006,779.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the recovery of oil from subterraneanformations by chemical flooding methods.

2. Description of the Prior Art

Petroleum is frequently recovered from subterranean formations orreservoirs by permitting the natural energy of the reservoir to push thepetroleum up through wells to the surface of the earth. These processesare referred to as primary recovery methods since they use the naturalenergy of the reservoir. However, a large amount of oil, generally inthe range of 65-90% or more, is left in the subterranean formation atthe conclusion of the primary recovery program. When the naturalreservoir energy is unable to produce more petroleum, it is a commonpractice to resort to some form of supplemental recovery technique inorder to recover additional petroleum left in the subterraneanformation. These supplemental operations are normally referred to assecondary recovery operations. If this supplemental recovery operationis the second in a series of such operations, it will be referred to asa tertiary recovery operation. However, the terminology is unimportantfor the purposes of this application and relates only to the sequence inwhich they are carried out.

The most widely used supplemental recovery technique because of its easeof implementation and low capital outlay is water flooding throughinjection wells drilled into the subterranean formation. In a waterflooding operation, the injected fluid displaces oil through theformation to be produced from the injection well. A major disadvantageto water flooding, however, is its relatively poor displacementefficiency largely due to the fact that water and oil are immiscible atreservoir conditions and high interfacial tension exists between theflood water and the oil. For this reason, after a water flood, a largeportion of the oil is still left unrecovered in the reservoir.

It has been recognized by those skilled in the art that a solutioneffecting a reduction in this interfacial tension between water and oilwould provide a much more efficient recovery mechanism. Therefore, theinclusion of a surface active agent or surfactant in the flood water wasrecognized as an acceptable technique for promoting displacementefficiency of the reservoir oil by the water. For example, U.S. Pat. No.3,468,377 discloses the use of petroleum sulfonates in water floodingoperations and U.S. Pat. No. 3,553,130 discloses the use of ethyleneoxide adducts of alkyl phenols for the same purpose. The use in waterflooding operations of water soluble surface active alkaline earthresistant polyglycol ethers is disclosed in U.S. Pat. No. 2,233,381.Other specialized surfactants, as will be discussed later, have beendiscovered to have special properties useful in water floodingoperations such as a tolerance for high salinity and calcium, and/ormagnesium ion concentrations often found in reservoir waters.

However, field operations employing surfactants and surface activeagents in injected fluid have not always been entirely satisfactory dueto the fact that these materials are often adsorbed by the formationrock to a relatively high degree, resulting in an ever decliningconcentration of the materials as they progress through the reservoir.Therefore, large concentrations of surface active materials haveheretofore been necessary to maintain a sufficient concentration at theoil-water interface. Due to this, many proposed flooding operationsinvolving surface active materials have been uneconomical.

Another serious problem for any recovery technique involving the drivingof oil with a fluid is premature breakthrough of the injection fluid.This premature breakthrough indicates that the reservoir has not beenadequately swept of oil. The problem is often described in terms ofsweep efficiency as distinguished from the displacement efficiencydescribed above. Displacement efficiency involves a microscopic pore bypore efficiency by which water displaces oil, whereas sweep efficiencyis related to the growth portion of the reservoir which is swept andunswept by the injected fluid. A major cause of poor sweep efficiency isassociated with the fact that the injected fluid generally has a lowerviscosity than the displaced fluid (petroleum). Thus, the injected fluidhas a higher mobility and tends to finger through the oil, prematurelybreaking through to the production well.

One solution to this high mobility problem is to increase the viscosityof the driving fluid. A way to do this is to add polymeric organicmaterials to a driving water which has the effect of increasing theviscosity of the water, thereby increasing the sweep efficiency of thesupplemental recovery process. U.S. Pat. No. 3,039,529 and U.S. Pat. No.3,282,337 teach the use of aqueous polyacrylamide solutions to increasethe viscosity of the injected fluid thereby promoting increase sweepefficiency. Polysaccharides as taught in U.S. Pat. No. 3,581,824 havebeen used for the same purpose. These polymers are quite expensive andany polymer lost to adsorption on the reservoir matrix addssubstantially to the cost since additional polymer is required tomaintain a given viscosity.

The above described problems have been recognized by those skilled inthe art of oil recovery and certain sacrificial compounds have beenadded to pretreat the formation in order to decrease the adsorption ofsubsequently injected surfactants and/or polymers. For example, U.S.Pat. No. 3,414,054 discloses the use of aqueous solutions of pyridine;U.S. Pat. No. 3,469,630 discloses the use of sodium carbonate andinorganic polyphosphates, and U.S. Pat. No. 3,437,141 discloses the useof soluble carbonates, inorganic polyphosphates and sodium borate incombination with saline solution of a surfactant having both a high anda low molecular weight component. These materials have not beencompletely satisfactory from a standpoint of performance and economicshowever.

U.S. Pat. No. 3,384,171 to Parker discloses that unmodifiedlignosulfonates may be used as a preflush followed by a surfactantsolution. While this method provides an improvement over usingsurfactant alone, my invention provides an improvement in oil recoveryover the process of Parker. My copending application Ser. No. 715,957filed Aug. 19, 1976 claims unmodified lignosulfonates as sacrificialagents. The present invention provides an improvement over that process.

SUMMARY OF THE INVENTION

The invention is a process of producing petroleum from subterraneanformation having an injection well and a production well incommunication therewith. The process comprises injecting into theformation via the injection well an aqueous solution of oxidizedlignosulfonate salts in admixture with a chemical oil recovery agent,for example, surfactant, polymer and/or a micellar dispersion. It is theusual practice to then inject a fluid such as water to sweep thechemical components through the reservoir to the production well,thereby displacing oil from the subterranean formation to the surface ofthe earth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A sacrificial material is injected by the process of this inventionthrough an injection means comprising one or more injection wells into asubterranean petroleum-containing formation to preferably occupy orcover all potential adsorption sites of the rock within the subterraneanformation thereby reducing the extent of adsorption of the moreexpensive chemical oil recovery agent injected therewith. A sacrificialagent performs best when it exhibits high adsorption on active sites ofrock surfaces, and thus diminishes surfactant and/or polymer adsorption.Chemical compounds of polyelectrolytic nature have the proper physicochemical and structural requirements to behave as successful sacrificialagents. The functional group on the sacrificial agent molecules enhancesadsorption either by hydrogen bonding or electrostatic attraction toactive sites on the rock surfaces.

A satisfactory sacrificial material has at least three importantcharacteristics. First, it should be less expensive than the surfactanton a cost effectiveness basis since it is to be sacrificed or adsorbedby the formation, probably not to be recovered. Next, it must beadsorbed readily by the subterranean formation matrix. Preferably thesacrificial material should be adsorbed more readily than the chemicaloil recovery agent to be used in the process. The third importantcharacteristic of a sacrificial agent is that the presence of suchadsorbed sacrificial material should retard or eliminate adsorption ofthe surfactant and/or polymer chemical recovery material on theadsorption sites of the formation rock. By adsorption sites of theformation rock it is meant those parts of the surfaces of the pores ofthe formation rock capable of adsorbing a chemical compound from asolution on contact.

The sacrificial material may not have a detrimental effect on therecovery efficiency of the chemical flooding operation. Additional oilis usually recovered only if the sacrificial material is followed by oris admixed with a surfactant and/or a polymer chemical recovery agentwhich will effectively increase the amount of oil displaced from thesubterranean formation. When the surfactant is chosen as the chemicalrecovery agent it should be injected in admixture with the sacrificialagent for best results and ahead of the following flooding water therebyachieving the desired interfacial tension reduction between the injectedfluid and the displaced fluid with minimal loss of surfactant on theformation matrix. The surfactant may be present in a hydrocarbon solventor in an aqueous solution or in a combination thereof. Any anionic,nonionic and/or cationic type of surfactant known in the art may be usedin the practice of this invention. Some types of surfactants werementioned previously. In addition, surfactants disclosed and claimed inthe following U.S. patents, for example, are particularly useful sincethey have been found to be capable of performing in reservoirs havingboth high salinities and high hardness levels: U.S. Pat. Nos. 3,858,656;3,811,505; 3,811,504 and 3,811,507.

Likewise, the amount of surfactant which must be employed in thepractice of any chemical flood is generally known in the art and is tobe found in published literature. However, the slug size of surfactantgenerally will range from about 0.01 to 1 pore volumes of an aqueoussurfactant solution having dissolved therein from about 0.01 to about10.0 percent by weight of the surfactant itself.

In my invention the sacrificial agent is preferably injected inadmixture with the surfactant slug into the petroleum formation. Thissurfactant/sacrificial agent mixture may or may not be preceded by aslug of sacrificial material in aqueous solution only. It has been foundthat this technique is superior to the preflush method of injecting aslug of sacrificial material followed by a slug of surfactant solutionwithout sacrificial material. However, the preflush method is superiorto using no sacrificial material at all.

In any of these embodiments and others which are obvious to thoseskilled in the art, the surfactant containing slug may be followed by amaterial to taper the viscosity before drive water is injected. Thistechnique known well to those skilled in the art prevents the water fromfingering into the more viscous surfactant containing slug.

In a specific embodiment of this invention, a sacrificial materialcomprising oxidized lignosulfonate salts, is injected via the suitableinjection means, i.e. through one or more injection wells completed inthe subterranean hydrocarbon formation, in admixture with a surfactantsolution. By injecting the sacrificial material and surfactant togetheroil recovery is maximized. The oil recovery is greater than preflushingthe formation with sacrificial agent and followed with surfactantsolution.

Another embodiment of my invention is the use of modifiedlignosulfonates in conjunction with an emulsion of water, hydrocarbonand surfactant, i.e., a micellar dispersion. The same parameters asdiscussed above for simple aqueous surfactant solutions would apply tomicellar dispersions. Micellar dispersions are known in the art. See forexample, U.S. Pat. No. 3,536,136 incorporated here by reference.

The sacrificial agents useful in the process of my invention areoxidized lignosulfonate salts. Lignosulfonates are anionicpolyelectrolytes soluble in water and tolerate hard water (polyvalentions, e.g. calcium and magnesium). They are also thermally stable informations where the temperature is high. Lignosulfonates aremacro-molecules built up by complex condensation of phenyl propaneunits. The sulfonate groups are attached to the aliphatic side chain,mainly to alpha carbon. Lignosulfonates are water soluble with molecularweights ranging from several thousand to around 50,000 or more. They areeconomically attractive since being by-products of the pulping industry,they are plentiful and cost less than either the surfactants or thepolymers used in enhanced oil recovery methods. The polyelectrolytelignosulfonates with strongly ionized sulfonate groups are negativelycharged species and have a tendency to adsorb on solid surfaces therebyimparting a negative charge to them. The rock surfaces of a reservoirtreated with lignosulfonate will be inert towards the anionicsurfactants in the flood water and therefore loss of surfactants to therock surfaces will be kept to a minimum. The same phenomenon will occurwith the polymer thickened drive fluid.

Lignin is second only to cellulose as the principal constituent in wood.Generally, lignin is a complex phenolic polyether containing manydifferent functional groups including carboxyls, carbonyls, andalcoholic and phenolic hydroxyls. Lignins and their derivatives aredescribed in Kirk-Othmer Encyclopedia of Chemical Technology, SecondEdition, Vol. 12, beginning at page 362. This publication describes twovery broad classes of lignin derivatives: sulfite lignins and alkalilignins.

The difference in the lignins exists because of the method of extractionof lignin material from woody materials. Sulfonates alkali lignins arereadily available commercially from various sources including but notlimited to West Virginia Pulp and Paper Company under the trade nameREAX. Their general method of preparation is described in theEncyclopedia of Chemical Technology referred to above. Briefly,sulfonated alkali lignins are prepared by cooking woodchips with a 10%solution of a mixture of sodium hydroxide with about 20 mole percent ofsodium sulfide. The lignin with wood is modified into a sodium compoundoften termed sodium lignate or alkali lignin which is very soluble inthe strongly alkaline solution. These alkali lignins are removed fromsolution by lowering the pH which precipitates out the alkali lignins.These unsulfonated alkali lignins are solid under various tradenamesincluding INDULIN. These alkali lignins are used to prepare thesulfonated derivatives. Methods of sulfonation are known by thoseskilled in the art. One typical method involves treating the alkalilignins with a solution of alkali sulfites at elevated temperature andpressure. The degree of sulfonation may be controlled to provide avariety of sulfonated alkali lignins.

The other main type of lignin derivatives are called sulfite lignins orsulfite lignosulfonates. Sulfite lignins are generally made by cookingwoodchips under pressure in a solution of sulfurous acid and calcium,magnesium, sodium or ammonium bisulfite. This process converts insolublelignins to soluble lignosulfonic acid. The lignosulfonic acids orcalcium, magnesium, sodium or ammonium salts of the lignosulfonic acidsare available under various tradenames including MARASPERSE, LIGNOSITE,ORZAN, TORANIL, and RAYFLO.

The broad term lignosulfonates used herein refers to both sulfonatedalkali lignins and sulfite lignosulfonates (sulfite lignins). These aredistinct types of compounds as explained above. Since the alkali ligninsrequire sulfonation after extraction of the material from woody productsit is proper to call them sulfonated alkali lignins. Likewise sincesulfite lignins emerge from the extraction process already sulfonated itis proper to refer to this class of materials as sulfite lignins orsulfite lignosulfonates.

My invention is the use of sulfonated alkali lignins and sulfitelignosulfonates, each modified by oxidation. Lignosulfonates havingdegrees of sulfonation from about 2.0 to saturation are acceptable asstarting materials for the modified lignosulfonates of my invention.Cations which are acceptable include Na⁺, K⁺, NH₄ ⁺, Ca⁺⁺, and Mg⁺⁺. Thedegree of sulfonation is the weight percentage of sulfonate (SO₃ ⁻)compared to the total molecular weight.

Crude unmodified lignosulfonates may be made with either softwoods orhardwoods. Although having basically the same functional groups thecrude unmodified softwood lignosulfonates have more sulfonate andhydroxyl groups than the crude unmodified hardwood lignosulfonates.Thus, in general, crude unmodified softwood lignosulfonates have betterhard water (Ca⁺⁺, Mg⁺⁺) tolerance than the hardwood form.

The term oxidized or oxidation for purposes of this disclosure refer tothose reactions which have the following effect on the unmodifiedlignosulfonate molecule. Oxidation of the unmodified lignosulfonatesresults in the formation of carboxyl groups from carbonyl groupings,alcoholic hydroxyl groups and at least a portion of terminal --CH₃groupings on alkyl side chains and also by a demethylation of at least aportion of the methoxy groupings which appear as a portion of the ringstructure. Oxidation also results in conversion of aromatic methoxygroups to form phenolic groups.

Air, air enriched with oxygen and/or oxygen is useful for oxidation ofthe unmodified lignosulfonate molecule as described above.Alternatively, where air, enriched air or oxygen will not produce theoxidative effects noted above it has been found necessary to reactunmodified lignin type materials with an oxygen containing gas whichalso contains ozone. U.S. Pat. No. 3,726,850 describes such a reactionscheme on lignin type materials. The disclosure of U.S. Pat. No.3,726,850 is incorporated herein by reference to the extent that itdescribes the effect of oxidation on a lignin type molecule (whicheffects would also be applicable to lignosulfonates). The reactionconditions described in U.S. Pat. No. 3,726,850 may or may not bealtered somewhat when reacting with a lignosulfonate instead of a ligninto obtain the same effects on the molecule.

Reactions such as lignosulfonates with chromate or dichromate and thelike are not within the scope of this disclosure or the term oxidized asmay be used in the claims appended hereto.

My invention includes the lignosulfonates which are oxidized as well asthe oxidized lignosulfonates which have been further reacted with methylsulfonate, chloroacetic acid and/or carbon dioxide.

Generally, the reaction with methyl sulfonate adds methyl sulfonategroups to the ortho sites of aryl groups present. Further details may befound in my copending application Ser. No. 745,494 filed of even date.

Generally, chloroacetic acid reacts with hydroxyl and sulfonate groupsto yield carboxylate groups. Further detail may be found in my copendingapplication Ser. No. 745,495 filed of even date now abandoned.

Reaction with carbon dioxide generally adds carboxylate groups to theortho sites on aryl groups. Further detail may be found in my copendingapplication Ser. No. 745,495 filed of even date now abandoned.

The quantity of oxidized lignosulfonates to be injected into thesubterranean hydrocarbon formation may be any amount up to and includingan amount sufficient to occupy substantially all of the active sites ofthe formation matrix. If less than the maximum amount is used, therewill be a corresponding increase in the adsorption of surfactant frominjection solution onto the formation matrix although the amount ofincrease will not be as great as in the case where the formation iscompletely free of oxidized lignosulfonate salts. At a maximum, only theamount of modified lignosulfonate salts needed to completely occupy theactive sites on the formation matrix is needed. The detriment resultingfrom using excess modified lignosulfonate salts would be an increase inthe cost of operating the oil recovery program.

The amount of oxidized lignosulfonate salts needed in the process of theinvention depends on the particular formation, the area or pattern to beswept and other formation characteristics. Those skilled in the art candetermine the exact quantity needed to afford the desired amount ofprotection.

Generally it has been found that the amount of oxidized lignosulfonatein the surfactant slug will be effective in amounts of from about 0.01to about 10.0 percent by weight of the total surfactant solution(including the aqueous portion). Total oxidized lignosulfonate will beeffective at the above concentrations in amounts ranging from 0.01 to1.0 pore volumes of the aqueous solution of surfactant-sacrificial agentor only sacrificial agent solution.

The effectiveness of this invention for reducing the adsorption ofsurfactant or polymer on formation rock and chemical flooding operationsis demonstrated by the following examples which are presented by way ofillustration and are not intended as limiting the spirit and scope ofthe invention as defined in the claims.

The following Examples demonstrate the performance of modifiedlignosulfonates in oil recovery from crushed limestone packs or sandpacks in the laboratory.

EXAMPLE I

The starting crude lignosulfonates were either hardwood or softwoodproducts. The calcium salt was converted to sodium salt to evaluate theeffect of this modification step. Lignosulfonates were modified byperforming reactions such as carboxylation by oxidation, carboxylationby chloroacetic acid, sulfomethylation and carboxylation by reactionwith carbon dioxide. Each reaction yields products with differentfunctional groups. The types of functional groups obtained by eachreaction are additive, and those affect both the tolerance oflignosulfonates to brine and the affinity of lignosulfonates to adsorbon surfaces of interest. The choice of an adsorbent to be used in theevaluation of sacrificial agents is important. For accurate evaluation,one must utilize adsorbents which allow high surfactant adsorption.

To compare the effectiveness of various lignosulfonates as sacrificialagents the single surfactant system sulfonated four mole ethylene oxideadduct of dodecyl phenol was used. Shake bottle tests were performed toevaluate the mitigation of surfactant adsorption to precipitated CaCO₃at 77 kg/m³ TDS and 43° C. Adsorption values of Adduct D-40CS* with orwithout lignosulfonates present are tabulated below:

    __________________________________________________________________________    Surfactant System                                                             10 kg/m.sup.3 Adduct D-40CS             mg Surfactant Adsorbed                + 10 kg/m.sup.3 Lignosulfonate                                                              Description               g CaCO.sub.3                          __________________________________________________________________________    No Lignosulfonate                       22.8                                  Norlig 42Z    Na salt; Hardwood; Carboxylated by Oxidation                                                            6.5                                   Norlig 42CAA  Na salt; Hardwood, Carboxylated by Chloroacetic                                                         12.0                                  Norlig 42ZCAA Na salt; Hardwood, Carboxylated by Oxidation                                  and Chloroacetic acid     5.0                                   Norlig 92Z    Na salt; Softwood, Carboxylated by Oxidation                                                            1.0                                   Norlig 92CAA  Na salt; Softwood, Carboxylated by Chloroacetic                                                         9.7d                                  Norlig 92ZCAA Na salt; Softwood, Carboxylated by Oxidation                                  and Chloroacetic acid     0.5                                   Norlig 41ZCAA Ca salt; Hardwood, Carboxylated by Oxidation                                  and Chloroacetic acid     10.4                                  Norlig 91ZCAA Ca salt; Softwood, Carboxylated by Oxidation                                  and Chloroacetic acid     1.0                                   Norlig 51 S-Z Ca salt; Softwood, Sulfomethylated, Carboxylated                              by Oxidation              4.1                                   __________________________________________________________________________

Results indicate that the softwood lignosulfonate derivatives exhibitgreater mitigation of surfactant adsorption than the hardwoodlignosulfonate derivatives when CaCO₃ is used as adsorbent. Conversionfrom Ca salt to Na salt has a moderate beneficial effect on theeffectiveness of the product. Improved tertiary oil recovery efficiencyachieved when lignosulfonates are incorporated into surfactant systemsmay not be solely due to a sacrificial agent effect. In addition tomitigation of surfactant adsorption on pore surfaces, other mechanismsmay also contribute to an improved oil recovery efficiency of asurfactant system.

EXAMPLE II

Modified lignosulfonates exhibit high sacrificial agent activity whenexposed to calcium carbonate surfaces in shake bottle tests. Fourdifferent reaction have been employed to obtain derivatives oflignosulfonates.

(A) Oxidation reaction

(B) Chloroacetic acid reaction

(C) Sulfomethylation reaction, and

(D) Carbon dioxide reaction.

Modified lignosulfonates with several types of functional groups can beprepared by employing any one of the above reactions or combinations ofthese reactions. The availability of modified lignosulfonates withdifferent types of functional groups is desirable because the morefunctional groups lignosulfonates have, the greater tolerance to highersalinity and hardness brines. The presence of different types offunctional groups (both polar and nonpolar) on lignosulfonates shouldcontribute to the attractive forces on substrates and enhance thesacrificial agent activity of these compounds.

The surfactant system (as in Example I) (with or withoutlignosulfonates) was used to determine relative sacrificial agenteffectiveness of lignosulfonates on precipitated calcium carbonate.Shake bottle tests were performed to evaluate surfactant adsorptionmitigation at 77 kg/m³ TDS and 43° C. Several adsorption values ofAdduct D-40CS with or without lignosulfonates present are tabulatedbelow:

    ______________________________________                                        Surfactant System                                                             10 kg/m.sup.3 Adduct D-40CS                                                       +                mg Surfactant Absorbed                                   10 kg/m.sup.3 Lignosulfonate                                                                       g CaCO.sub.3                                             ______________________________________                                        No sacrificial agent 21.6                                                     Norlig 92g                                                                    (Softwood:unmodified, Na salt)                                                                     17.5                                                     Norlig 92Z                                                                    (Softwood:oxidized, Na salt)                                                                        1.0                                                     Norlig 41ZCAA                                                                 (Hardwood:oxidized, carboxylated,                                                                  10.4                                                     Ca salt)                                                                      Norlig 41SCAA                                                                 (Hardwood:sulfomethylated,                                                    carboxylated, Ca salt)                                                                             11.3                                                     Norlig 91ZCAA                                                                 (Softwood:oxidized, carboxylated                                              Ca salt)              1.0                                                     Norlig 91SCAA                                                                 (Softwood:sulfomethylated,                                                    carboxylated Ca salt)                                                                               6.0                                                     ______________________________________                                    

It is observed that the oxidized and carboxylated lignosulfonates aremore effective sacrificial agents here than the sulfomethylated andcarboxylated ones. This is true for both the hardwood and softwoodderivatives. It is to be noted that the softwood modifiedlignosulfonates exhibit greater surfactant adsorption inhibition onCaCO₃ than the hardwood modified lignosulfonates. This is probably dueto the fact that the softwood degree of sulfonation is higher than thehardwood degree of sulfonation.

Since various structural forms of modified lignosulfonates areavailable, it is possible to prepare modified lignosulfonates whichshould exhibit high surfactant adsorption mitigation for a givensurfactant system on a substrate of interest such as limestone,sandstone and others.

EXAMPLE III

Derivatives of lignosulfonates exhibit varying degrees of sacrificialagent activity when calcium carbonate is used as substrate. Oxidized andcarboxylated lignosulfonates have been tested for surfactant adsorptionmitigation. In this investigation sandstone (Dog Lake EE sand) was usedto determine how structural differences of modified lignosulfonatesaffect their performance as sacrificial agents on sandstone.

The surfactant (as in Examples I and II) was used in surfactant systemswhere the salinity was maintained at 77 kg/m³ TDS and the temperature at43° C. Quantities of 50 g of sandstone were exposed to 50 cc surfactantsolutions to achieve large enough surfactant concentration changes foraccurate adsorption value determinations. Bottles containing themixtures were shaken for 24 hours and then they were equilibrated for 3days prior to centrifugation, which was done to effectively separate theadsorbent from the equilibrium solutions. Several adsorption values ofsystems composed of 10 kg/m³ (1%, w/v) surfactant and 10 kg/m³ (1%, w/v)lignosulfonate are tabulated below:

    ______________________________________                                                             mg Surfactant Adsorbed                                   Lignosulfonates      g Dog Lake EE Sand                                       ______________________________________                                        No sacrificial agent 1.5                                                      Norlig 92g (Softwood:unmodified)                                                                   1.1                                                      Norlig 92Z (Softwood:oxidized                                                 Na salt)             0.8                                                      Norlig 92ZCAA (Softwood:oxidized,                                             carboxylated, Na salt)                                                                             0.7                                                      Norlig 42Z (Hardwood-oxidized,                                                Na salt)             0.5                                                      Norlig 42ZCAA (Hardwood-oxidized,                                             carboxylated, Na salt)                                                                             0.4                                                      ______________________________________                                    

The adsorption tests indicated that both the oxidized and the oxidizedand carboxylated lignosulfonates have greater effectiveness assacrificial agents on sandstone substrates than the unmodifiedlignosulfonate. Results also indicate that both the oxidized and theoxidized and carboxylated hardwood lignosulfonates are more effectivethan the corresponding softwood lignosulfonates as sacrificial agentswhere sandstone is used as adsorbent. For CaCO₃ as adsorbent oxidized oroxidized and carboxylated softwood lignosulfonates were more effectivesacrificial agents than oxidized or oxidized and carboxylated hardwoodlignosulfonates.

The differences in performance between the hardwood and softwoodderivatives can possibly be explained on the basis of their chemicalstructures. Softwood lignosulfonates are predominantly of the guaiacylstructure, whereas hardwood lignosulfonates have both the guaiacyl andthe syringyl structures. The major feature of the oxidation reaction isthe conversion of methoxyl groups (inactive) to phenolic groups(active). Thus, oxidized hardwood lignosulfonates have more phenolicgroups because the syringyl structure has twice as many methoxyl groupsthan the guaiacyl structure. Hydrogen bonding between the phenolicgroups of the oxidized lignosulfonates and the oxygens of the sandstonesurfaces is a probable mechanism contributing to the enhanced adsorptionof oxidized lignosulfonates on sandstone. It should be emphasized thatelectrostatic attraction between the anionic functional groups(sulfonates and carboxylates) on the modified lignosulfonates andsandstone surfaces also contributes to the adsorption of theselignosulfonates.

The following examples (IV-VIII) demonstrate the performance of modifiedlignosulfonates in oil recovery from crushed limestone packs or sandpacks in the laboratory. In those tests the packs were saturated withoil and then water flooded to a residual oil saturation. Then thesurfactant solutions were injected followed by polymer solutions.

EXAMPLE IV

    ______________________________________                                        OIL RECOVERY FROM CRUSHED LIMESTONE PACKS                                     Surfactant                                                                    System: 0.4% Dodecylbenzene sulfonate + 0.6 %                                         Sulfonated 4 mole EO adduct of nonyl phenol                                   + 1.0% Lignosulfonate in 65,000 ppm TDS brine                         Polymer:                                                                              0.1% Polysaccharide polymer B-1459 in                                         65,000 ppm TDS brine                                                              % Pore                                                            Sulfomethy- Volume     % Pore Volume                                                                             % Tertiary                                 lated Ligno-                                                                              Surfactant Polymer     Oil                                        sulfonates  Injected   Injected    Recovery                                   ______________________________________                                        None        20         50          62.8                                       Marasperse BS-22-3                                                            (Sulfomethylated                                                              Na salt)    20         50          91.0                                       Marasperse 22 S-Z                                                             (sulfomethylated                                                              and oxidized Na                                                               salt)       20         50          88.6                                       ______________________________________                                    

EXAMPLE V

    ______________________________________                                        Surfactant                                                                    System: 1% Sulfated 4 mole EO adduct of nonyl phenol                                  + 1% Lignosulfonate in 180,000 ppm TDS brine                          Polymer:                                                                              0.1% Polysaccharide polymer B-1459                                            in 180,000 ppm TDS brine                                                          % Pore                                                            Sulfomethy- Volume     % Pore Volume                                                                             % Tertiary                                 lated Ligno-                                                                              Surfactant Polymer     Oil                                        sulfonates  Injected   Injected    Recovery                                   ______________________________________                                        None        15         50          60.0                                       Marasperse BS-22-6                                                            (sulfomethylated                                                              Na salt)    15         50          76.7                                       Marasperse 22S-Z                                                              (Sulfomethylated                                                              and oxidized Na                                                               salt)       15         50          79.4                                       Norlig 41S-2Z                                                                 (sulfomethylated                                                              and oxidized                                                                  Ca salt)    15         50          78.0                                       ______________________________________                                    

EXAMPLE VI

    ______________________________________                                        OIL RECOVERY FROM DOG LAKE SAND PACKS                                         Surfactant                                                                    System: 2.0% Petroleum sulfonate                                                      + 0.6% sulfonated 6 mole EO adduct nonyl                                      phenol                                                                        + 1% Lignosulfonate in 105,000 ppm TDS brine                          Polymer:                                                                              0.1% Polysaccharide polymer B-1459                                    Sulfomethy-  % Pore                                                           lated and    Volume    % Pore Volume                                                                             % Tertiary                                 Carboxylated Surfactant                                                                              Polymer     Oil                                        Lignosulfonate                                                                             Injected  Injected    Recovery                                   ______________________________________                                        None         25        100         65.8                                       Norlig 42SCAA                                                                              25        100         82.1                                       Na salt, hardwood                                                             sulfomethylated then                                                          reacted with chloro-                                                          acetic acid                                                                   ______________________________________                                    

EXAMPLE VII

    ______________________________________                                        OIL RECOVERY FROM DOG LAKE SAND PACKS                                         Surfactant                                                                    System:   2.0% Petroleum sulfonate + 0.6% sulfon-                                       ated 6 mole EO adduct of nonyl phenol                                         + 1% Lignosulfonate in 105,000 ppm TDS                                        brine                                                               Polymer:  0.1% Polysaccharide polymer B-1459                                  Carboxy-                                                                      lated      % Pore Volume                                                                             % Pore Volume                                                                             % Tertiary                                 Lignosul-  Surfactant  Polymer     Oil                                        fonate     Injected    Injected    Recovery                                   ______________________________________                                        None       25          100         65.8                                       Norlig 92CAA                                                                             25          100         80.0                                       Na salt, softwood                                                             carboxylated with                                                             chloroacetic acid                                                             ______________________________________                                    

EXAMPLE VIII

    ______________________________________                                        OIL RECOVERY FROM DOG LAKE SAND PACKS                                         Surfactant                                                                    System:   2.0% Petroleum sulfonate + 0.6% adduct                                        sulfonate 6 mole EO adduct of nonyl                                           phenol + 1% Lignosulfonate in 105,000 ppm                                     TDS brine                                                           Polymer:  0.1% Polysaccharide polymer B-1459                                  Oxidized                                                                      and Carboxy-                                                                             % Pore Volume                                                                             % Pore Volume                                                                             % Tertiary                                 lated Ligno-                                                                             Surfactant  Surfactant  Oil                                        sulfonate  Injected    Injected    Recovery                                   ______________________________________                                        None       25          100         64.5                                       Norlig 42ZCAA                                                                            25          100         84.1                                       Na salt, Hardwood                                                             oxidized then car-                                                            boxylated with                                                                chloroacetic acid                                                             ______________________________________                                    

I claim:
 1. In a method for recovering oil from a subterranean formationcontaining oil and having an injection well and a production wellwherein an aqueous surfactant solution is injected into the injectionwell in order to drive the oil to the production well wherein it isproduced the improvement which comprises:injecting into the injectionwell in admixture with the surfactant oxygen or ozone oxidizedlignosulfonates in an amount effective for reducing the extent ofadsorption of the surfactant by the formation matrix.
 2. A method as inclaim 1 wherein the lignosulfonates have a degree of sulfonation rangingfrom about 2.0 to saturation.
 3. A method as in claim 1 wherein thecation of the lignosulfonate salts is selected from the group consistingof calcium, magnesium, sodium, potassium, and ammonium.
 4. A method asin claim 1 wherein the lignosulfonate salts are present in amountsufficient to occupy substantially all of the active sites on theformation matrix.
 5. A method for recovering oil from a subterraneanformation containing oil and having an injection well and a productionwell wherein flooding water is injected into the subterranean formationcomprising:(a) injecting through the injection well into the formationan aqueous solution of oxidized lignosulfonates, (b) subsequentlyinjecting into the formation via the injection well an aqueoussurfactant solution also containing oxygen or ozone oxidizedlignosulfonates said oxidized lignosulfonates of steps (a) and (b) beingpresent in amounts effective for reducing the extent of adsorption ofthe surfactant by the formation matrix and (c) producing oil from theformation via the production well.
 6. A method as in claim 5 wherein thesolution step (b) is followed by flooding water.
 7. A method as in claim5 wherein the oxidized lignosulfonates have a degree of sulfonationranging from about 2.0 to saturation.